We've covered this before but since you apparently have the contextual recall of a gnat let's try again.
There absolutely is uncertainty in drafting players. What one is hoping for is to limit the outright busts to outlier status. They are MUCH better at this than you are since your wins are the outliers and busts are the norm.
If "they" didn't know what they were doing the following wouldn't be the case. (breakdown of 2016 Pro Bowl)
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Want the really big picture? Scope out this site and look at the first two rounds vs all the others. Take special note of the huge 1st round count.
Hall of Famers by Draft Round - Hall of Famers | Pro Football Hall of Fame Official Site
Finally lets scope out your own special "Picks I hated" list.
1. Jared Goff to the Rams.
Goff is in the top 10 in both yardage and rating while helming the league's #2 scoring offense.
2. Joey Bosa to the Chargers
DROTY who already has his jersey in Canton for racking up more sacks in his first 20 games than anyone in the history of the game. No one trick pony either as he's also tied for 4th in the league in combined tackles for DE's.
3. Deforest Buckner to the 49ers.
[/FONT]Currently the league's 3rd leading tackler from the DT position.
4. Leonard Floyd to the Bears
Hasn't made you look completely the fool as much as the others but is still tied for #21 in the league in sacks from the LB position (2nd on the Bears)
And then of course there's Taylor and Hogan and Hackenberg, etc. Oh, and in all the hilarity of you picking Taylor as the #2 RB in that draft do you recall who you picked at #3? That'd be Jonathan Williams. The only thing keeping you from taking more of a beating on that pick is Taylor being even worse. Oh yeah, and of backs with at least 100 carries (the normal cutoff for sample size) Derrick Henry, another projected bust, is #4 in the league at RB in ypc.
This is just a sampling of how utterly and completely mythical the idea of you having any sort of special skill at spotting talent is, especially compared to people that make a living at such things.